Heavy vehicles, in particular commercial vehicles, are frequently equipped with a so-called engine brake to reduce or avoid overheating and wear of the mechanical wheel brakes during extended brake applications. A plurality of embodiments of the engine brake is known from the related art, e.g., a variable valve train or a decompression valve for blowing compressed air out of the cylinders of an internal combustion engine before the stored potential energy is again converted into kinetic energy. Further known from the related art is a throttle valve in the exhaust system of the internal combustion engine for increasing the exhaust gas backpressure, the internal combustion engine then operating as a pump against the exhaust gas pressure. Finally, in the case of turbochargers having variable turbine geometry, the exhaust gas backpressure can be increased by suitably activating the turbocharger.
An actuator is always necessary for operating the engine brake. The actuator cannot be positioned at any desired speed. If, after the engine brake is applied, the internal combustion engine is again operated, undesirably high exhaust gas pressures may arise in the exhaust tract, in particular in the case of a throttle valve and a turbocharger having variable turbine geometry. Excessively high pressure peaks may result in the destruction of the internal combustion engine or components in the exhaust system of the internal combustion engine. In particular, seals in the exhaust system may be destroyed or the throttle valve may be damaged; furthermore, excessively high exhaust gas backpressures may cause the exhaust valves to open and collide with the pistons, and in the case of turbochargers having variable turbine geometry, the turbocharger may be destroyed through excessive rotor speed.
In order to avoid too rapid a rise of the exhaust stream and accordingly of the exhaust gas (back) pressure until the engine brake is completely deactivated, the driver's torque request is delayed in engine brakes according to the related art. The delay of the driver's torque request means that even in the case of small driver inputs that do not result in any unacceptably high exhaust streams, the operating behavior is adversely affected because the responsiveness of the internal combustion engine is generally delayed between the time the engine brake is applied and the input of a new torque request by the driver.